During operation, many of the critical elements of building and engineering structures are in difficult operating conditions (high temperature, aggressive environment, etc.). In this case, they may be subject to a double effect: corrosion and material damage. Corrosion leads to a reduction in the cross-section of a structure, resulting in stress increase therein. In turn, the damage to the material is accompanied by the appearance of microcracks and voids therein due to inelastic deformation (creep), which leads to a deterioration of physical characteristics of the material (for example, elastic modulus) and a sharp decrease in the stress values at which the structure is destroyed. This paper considers the optimization of bending rectangular cross-section elements operated in conditions conducive to the appearance of both corrosion and material damage. As the equation of corrosion, the model of V. M. Dolinsky is taken. This model takes into account the effect of stresses on the corrosion wear of structures. As a kinetic equation describing the change in material damage, the model of Yu. N. Rabotnov is used. The optimality criterion is the minimum mass of the structure. The height of the rectangular cross-section bending element along its length is optimized using the principle of equal damage at the final moment of the lifetime of the structure. The proposed approach can be used to solve similar problems of the optimal design of structures operating in conditions of corrosion and material damage with the use of both analytical solutions and numerical methods.